The present invention relates to a sliding-vane type oil free rotary compressor for compressing gas and gas-liquid mixtures, and more particularly to such a compressor that is utilizable as a supercharger for a vehicle internal-combustion engine, an air pump, and a frigerant compressor, which are required to run at a wide range of rotary speeds and at a large flow rate.
In general, compressors have differing problems depending upon their applications. In the case of compressors for the compression of compressible fluid, the most important problem is a temperature rise which results from both adiabatic compression and from sliding friction. For example, the high compression ratio and large flow rate compressor has its temperature elevated up to about 250.degree. C., exceeding the tolerable temperature of the compressor's parts such as the vane, cylinder, bearing, and seal member. Oil lubricated type compressors have their frictional parts lubricated as well as cooled by oil. But, they cannot be used as superchargers for an internal-combustion engine because of the necessary requirement of requiring a device for recovering oil from the discharge fluid.
Oil free type rotary compressors, having neither lubricating oil nor cooling effect by oil, should minimize heat generated from sliding friction irrespective of unavoidable heat developed from adiabatic compression. The sliding friction between the apex of the vane and the inner surface of the cylinder produces heat more than any other frictional parts. In order to reduce the sliding friction, Japanese Published Unexamined Patent Applications (Kokai Tokkyo Koho) Nos. 52-71713 and 56-18092 have disclosed a compressor comprising a rotary sleeve rotatably mounted in the cylinder and floatingly supported by oil. The rotary sleeve rotates together with the rotor to prevent the apex of each vane from sliding on the inner surface of the rotary sleeve. However, the compressor as disclosed above is unsuitable as a compressor required to run at a wide range of rotary speeds and have a relatively high compression ratio and a large capacity. The reason for this is that, although oil or incompressible fluid is effective to support the rotary sleeve in stationary running in which the fluid lubricating conditions are maintained, it inevitably accompanies a seizure due to lack of oil under the boundary lubricating conditions in the initial period of running, an oil leakage due to a high pressure produced in high speed running, and damage due to an abnormally high localized pressure.
The present invention is intended to solve the problem of how to design a compressor that can be used at a high compression ratio and a wide range of rotary speeds. According to the invention, the sliding-vane type oil free rotary compressor comprises a center housing, a rotary sleeve mounted in the center housing with the intervention of a pressure chamber, at least one high-pressure passage extending from a discharge chamber and opening to the pressure chamber through the intermediary of a throttle, and an exhaust port extending from the pressure chamber to a suction chamber or the atmosphere, whereby the rotary sleeve is floatingly supported by the dynamic pressure of a compressible fluid.
Accordingly, it is an object of the present invention to provide an improved compressor that is free from problems created by the use of oil or an incompressible fluid.
It is another object of the present invention to provide an improved compressor in which a rotary sleeve is floatingly supported by a compressible fluid.
Other objects of the present invention will appear in the following description and appended claims taken in connection with accompanying drawings.